Use of α,β unsaturated aliphatic aldehydes and ketones to inhibit potato tuber sprouting

ABSTRACT

The present invention provides methods for inhibiting sprouting of potato tubers, the methods each including the step of contacting a potato tuber with an amount of a chemical agent including at least one aliphatic carbonyl compound selected from the group consisting of a C 3  to C 14 , α,β unsaturated aliphatic aldehyde and a C 4  to C 14 , α,β unsaturated aliphatic ketone, wherein the amount of the chemical agent is effective to inhibit potato tuber sprouting. Some aldehydes and ketones useful in the practice of the present invention are defined by formulae I and II, respectively, as set forth herein. In the practice of the methods of the invention the chemical agent is applied after the potato tubers have been harvested, but typically not later than the onset of sprouting.

This application has been filed under 35 USC 371 as the national stageof international application PCT/US01/48907, filed Dec. 13, 2001, whichclaims benefit of Ser. No. 60/255,996, filed Dec. 14, 2000, and claimsbenefit of Ser. No. 60/301,862 filed Jun. 29, 2001.

FIELD OF THE INVENTION

This invention relates to the use of α,β unsaturated aliphatic aldehydesand ketones to inhibit sprouting of potato tubers.

BACKGROUND OF THE INVENTION

Potatoes destined for storage are subjected to wound healing immediatelyfollowing harvest, during the initial phase of the storage season.During this period, wound periderm develops over cuts and abrasions thatresulted from mechanical injury during harvesting. The healing periodallows for optimal skin set and suberization of cut surfaces, ultimatelyproviding a barrier against water loss and bacterial and fungalinfection. In general, the rate of wound healing is dependent upontemperature; healing occurring faster at higher temperatures. However,high temperature at the beginning of storage often stimulates pathogensand influences various physiological processes (e.g., respiration) thatcan lead to reduced storability for seed potatoes, fresh market potatoesand processing potatoes. Hence, the temperature selected for woundhealing is usually a compromise. Holding tubers at 10° C. to 15° C. forten to fourteen days under high humidity stimulates periderm developmentand suberization while minimizing the potential for tuber decay.

Storage temperature is lowered to holding levels after the healingperiod. The holding temperature depends on the market for which thetubers are destined. Fresh market tubers can be held at 4° C., ascold-induced sweetening is not a concern. This low temperaturestimulates reducing sugar accumulation, effects a relatively longdormant period, and results in the longest storage life. Nonetheless,potato tubers destined for purchase by consumers are often treated witha chemical sprout inhibitor early in the storage season, and may receiveanother treatment of sprout inhibitor before being bagged ready forshipment to retail outlets.

Potatoes that will be processed to make french fries or potato chips(i.e., processing potatoes) must be held at higher temperatures (around10° C.) to prevent buildup of reducing sugars. Accumulation of reducingsugars during storage at low temperatures reduces the quality ofprocessed potato products. In particular, heating during the deep-fryingprocess induces a non-enzymatic reaction between reducing sugars andamino acids, giving an undesirable color, flavor and texture to theprocessed product. Hence, buildup of sugars in potatoes stored at lowtemperature is a major problem for processors. Cold-induced sweeteningis avoided over the short term by storing tubers at a higher temperature(around 10° C.); however, in the absence of chemical sprout inhibitors,the ultimate storage life is greatly reduced by loss of dormancy andearly sprouting stimulated by the higher temperature. Thus, virtuallyall processing potatoes are treated with chemical sprout inhibitors.

Sweetening in stored processing potatoes can be at least partiallyreversed by a reconditioning process in which potato tubers are storedfor a one to three week period at a higher temperature of about 15° C.before being processed. The higher storage temperature stimulatesrespiration and the degradation of reducing sugars in the tubers. Higherstorage temperature, especially when applied toward the end of thenatural dormancy period of potato tubers, promotes sprouting, and sosprout inhibitors are typically applied during the reconditioningprocess.

The main sprout inhibitors registered for use on potatoes arechlorpropham (CIPC), maleic hydrazide (MH), and dimethylnaphthalene(DMN). Diisopropylnaphthalene (DIPN) has received an experimental usepermit to be used in combination with CIPC. The two chemicals incombination (CIPC plus DIPN) appear to be more effective at lowerconcentrations than either of the two chemicals alone.

The United States Environmental Protection Agency (EPA) considers CIPCas a group E chemical (evidence for non-carcinogenicity for humans).CIPC was originally registered in the U.S. as a pre- and post-emergenceherbicide in 1962 and the EPA has set residue limits for potato tubers.Notwithstanding the safety record of CIPC, the trend today is to reducethe use of synthetic pesticides in agriculture, and thus reduce chemicalresidues in the global food supply. CIPC is continually beingscrutinized by the EPA as it is among the three pesticides found in thehighest concentrations in the average American diet (Gartrell et al., J.Assoc. Off. Anal. Chem. 69:146-161 (1986)).

A need therefore exists for methods to inhibit potato tuber sproutingthat utilize environmentally benign chemicals, such as naturalphytochemicals.

SUMMARY OF THE INVENTION

In accordance with the foregoing, the present invention provides methodsfor inhibiting sprouting of potato tubers, the methods each includingthe step of contacting a potato tuber with an amount of a chemical agentincluding at least one aliphatic carbonyl compound selected from thegroup consisting of a C₃ to C₁₄, α,β unsaturated aliphatic aldehyde anda C₄ to C₁₄, α,β unsaturated aliphatic ketone, wherein the amount of thechemical agent is effective to inhibit potato tuber sprouting. Somealdehydes and ketones useful in the practice of the present inventionare defined by formulae I and II, respectively, as set forth herein.Typically, the chemical agent is applied simultaneously, orsubstantially simultaneously, to numerous, harvested, potato tubers. Inthe practice of the methods of the invention the chemical agent isapplied after the potato tubers have been harvested, but typically notlater than the onset of sprouting. In some embodiments of the methods ofthe invention, the amount of chemical agent is sufficient to provide adosage of the at least one aliphatic carbonyl compound of from 0.001mmol/kg potato tubers to 100 mmol/kg potato tubers.

The methods of the invention are useful for inhibiting sprouting ofpotato tubers in any situation in which sprouting inhibition is desired.For example, the methods of the invention are useful for inhibitingsprouting of potato tubers that are stored before being sold toconsumers, or to processors for making french fries or potato chips.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same become betterunderstood by reference to the following detailed description, whentaken in conjunction with the accompanying drawings, wherein:

FIG. 1A shows the percentage of plant emergence from potato tuberstreated with trans-2-hexenal (open circles), and from potato tubers thatwere not treated with trans-2-hexenal (filled circles).

FIG. 1B shows the effect of trans-2-hexenal on leaf dry weight of potatoplants germinated from potato tubers treated with trans-2-hexenal.

FIG. 1C shows the effect of trans-2-hexenal on the number of stemsgrowing from potato tubers treated with trans-2-hexenal.

FIG. 1D shows the effect of trans-2-hexenal on stem dry weight of potatoplants germinated from potato tubers treated with trans-2-hexenal.

FIG. 1E shows the effect of trans-2-hexenal on leaf area of potatoplants germinated from potato tubers treated with trans-2-hexenal.

FIG. 1F shows the effect of trans-2-hexenal on plant dry weight ofpotato plants germinated from potato tubers treated withtrans-2-hexenal.

FIG. 2A shows the effects of trans-2-pentenal, (C-5), trans-2-hexenal(C-6), trans-2-heptenal (C-7), trans-2-octenal (C-8) and trans-2-nonenal(C-9) on the number of sprouts that grew from Russet Burbank potatotubers following storage at 8° C. (46° F.), 95% relative humidity (RH),for 17 weeks. As described more fully in Example 5, four-month-oldtubers (previously stored at 4° C.) were treated (for 24 h) withdifferent concentrations of the aldehydes in mid January. The treatedtubers were then stored in the dark for 120 days (17 weeks).

FIG. 2B shows the effects of trans-2-pentenal, (C-5), trans-2-hexenal(C-6), trans-2-heptenal (C-7), trans-2-octenal (C-8) and trans-2-nonenal(C-9) on the number of sprouts that grew from Ranger Russet potatotubers following storage at 8° C. (46° F.), 95% relative humidity (RH),for 17 weeks. The tubers were treated as described in the legend to FIG.2A, and in Example 5.

FIG. 2C shows the effects of trans-2-pentenal, (C-5), trans-2-hexenal(C-6), trans-2-heptenal (C-7), trans-2-octenal (C-8) and trans-2-nonenal(C-9) on the fresh weight of sprouts that grew from Russet Burbankpotato tubers following storage at 8° C. (46° F.), 95% relative humidity(RH), for 17 weeks. As described more fully in Example 5, four-month-oldtubers (previously stored at 4° C.) were treated (for 24 h) withdifferent concentrations of the aldehydes in mid January. The treatedtubers were then stored in the dark for 120 days (17 weeks).

FIG. 2D shows the effects of trans-2-pentenal, (C-5), trans-2-hexenal(C-6), trans-2-heptenal (C-7), trans-2-octenal (C-8) and trans-2-nonenal(C-9) on the fresh weight of sprouts that grew from Ranger Russet potatotubers following storage at 8° C. (46° F.), 95% relative humidity (RH),for 17 weeks. The tubers were treated as described in the legend to FIG.2A, and in Example 5.

FIG. 3 shows the effects of trans-2-nonenal on reconditioning of RussetBurbank potatoes. Seven-month-old tubers from 4° C. (40° F.) storagewere treated with 0.45 mmol/kg trans-2-nonenal for 17 hours at 23° C.The tubers were then placed at 14° C. (57° F.) to recondition. Frenchfries were processed from the tubers through four weeks ofreconditioning. Fry color (lightness or darkness) was quantified with aphotovolt reflectance meter. High photovolt values indicatelight-colored fries (high processing quality). Low photovolt valuesindicate low-quality, dark-colored fries.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Unless specifically defined herein, all terms used herein have the samemeaning as they would to one skilled in the art of the presentinvention. U.S. provisional patent application serial No. 60/255,996,filed Dec. 14, 2000, and U.S. provisional patent application serial No.60/301,862, filed Jun. 29, 2001, are both incorporated herein byreference in their entirety.

As used herein, the term “potato tuber” refers to the undergroundstorage organ of the potato plant (Solanum tuberosum). The tuber is amodified stem and includes buds that can sprout and form new potatoplants.

The phrase “effective to inhibit sprouting” means that: (a) the number,and/or the weight, of stems growing from a defined number of potatotubers contacted with a chemical agent in accordance with the presentinvention is less than the number, and/or the weight, of stems growingfrom the same number of control potato tubers (of the same cultivar asthe treated potato tubers) that were not contacted with a sproutinginhibitor; and/or (b) the average rate of growth of stems growing from adefined number of potato tubers contacted with a chemical agent inaccordance with the present invention is less than the average rate ofgrowth of stems growing from the same number of control potato tubers(of the same cultivar as the treated potato tubers) that were notcontacted with a sprouting inhibitor. Control potato tubers are treatedidentically to potato tubers contacted with a chemical agent inaccordance with the present invention, except as otherwise described.

In accordance with the foregoing, in one aspect, the present inventionprovides methods for treating potato tubers, the methods each comprisingthe step of contacting a potato tuber with an amount of a chemical agentthat includes at least one aliphatic carbonyl compound selected from thegroup consisting of a C₃ to C₁₄, α,β unsaturated aliphatic aldehyde anda C₄ to C₁₄, α,β unsaturated aliphatic ketone, wherein the amount of thechemical agent is effective to inhibit potato tuber sprouting.

Some aldehydes useful in the practice of the present invention aredefined by formula I, and some ketones useful in the practice of thepresent invention are defined by formula II:

wherein:

-   -   the aliphatic aldehyde of formula I is C₃ to C₁₄;    -   the aliphatic ketone of formula II is C₄ to C₁₄;    -   R₁ is H or branched or unbranched, substituted or unsubstituted        C₁-C₁₁ lower alkyl, or branched or unbranched, substituted or        unsubstituted C₁-C₁₁ lower alkenyl;    -   R₂ is branched or unbranched, substituted or unsubstituted        C₁-C₁₁ lower alkyl, or branched or unbranched, substituted or        unsubstituted C₁-C₁₁ lower alkenyl; and    -   R₃ is H or branched or unbranched, substituted or unsubstituted        C₁-C₁₀ lower alkyl, or branched or unbranched, substituted or        unsubstituted C₁-C₁₀ lower alkenyl.

“Substituted” refers to the replacement of hydrogen with a monovalent ordivalent radical. Suitable substitution groups include, for example,hydroxyl, nitro, amino, imino, cyano, halo, thio, thioamido, amidino,imidino, oxo, oxamidino, methoxamidino, imidino, guanidino, sulfonamido,carboxyl, formyl, loweralkyl, haloloweralkyl, loweralkoxy,haloloweralkoxy, loweralkoxyalkyl, alkylcarbonyl, arylcarbonyl,aralkylcarbonyl, heteroarylcarbonyl, heteroaralkylcarbonyl, alkylthio,aminoalkyl, cyanoalkyl, and the like.

Some chemical agents useful in the practice of the methods of theinvention consist essentially of a single aliphatic carbonyl compounddefined by formula I or by formula II. Some chemical agents useful inthe practice of the methods of the invention include two or morealiphatic carbonyl compounds defined by formula I and/or by formula II.Some chemical agents useful in the practice of the methods of theinvention include one or more aliphatic carbonyl compounds defined byformula I and/or by formula II, but do not include a chemical compoundnot encompassed by formula I or formula II. Non-limiting examples ofuseful aliphatic aldehydes defined by formula I include:trans-2-pentenal; trans-2-hexenal; trans-2-heptenal; trans-2-octenal;trans-2-nonenal; trans-2-decenal; trans-2-undecenal; trans-2-dodecenal;trans-2,4,-nonadienal; trans-2, cis-6-nonadienal; trans-3-nonen-2-one.Some chemical agents useful in the practice of the methods of theinvention include at least one aliphatic carbonyl compound defined byformula I or by formula II, and also include at least one other compoundthat possesses the ability to inhibit potato tuber sprouting (e.g.,chlorpropham, maleic hydrazide, diisopropylnaphthalene,dimethylnaphthalene, carvone, eugenol, benzothiazide, ethylene, aromaticacids (e.g., anisic acid, coumaric acid, gallic acid), rape oil methylester, medium and long-chain alcohols, jasmonates, aromatic aldehydes(e.g., benzaldehyde, salicaldehyde, cinnamaldehyde, hydrocinnamaldehyde,cuminaldehyde, thymol), monoterpenes (e.g., cineole, fenchone, menthol),and essential oils (e.g., mint oils)).

In the practice of the methods of the invention the chemical agent isapplied after the potato tubers have been harvested, but typically notlater than the onset of sprouting. Thus, in some embodiments of themethods of the invention, the chemical agent is applied to the tuberswithin one, two, three, four five, six, seven or eight weeks after thetubers are harvested. Typically, the chemical agent is applied beforethe end of the natural dormancy period of the harvested potato tubers,i.e., before the buds on the potato tubers have begun to sprout.Preferably the chemical agent is applied as close to the end of thenatural dormancy period as is practical. The duration of the naturaldormancy period is known to those of skill in the art and varies betweenpotato cultivars, and depends on such factors as the physiology andcondition of the tubers at harvest, and the storage temperature. Forexample, Table 1 shows estimates (in days) of the natural dormancyperiod of specific potato cultivars stored at specified temperatures.

TABLE 1 Dormancy period when Dormancy period when Potato cultivar storedat 48° F. stored at 45° F. Russet Burbank ˜130 days ˜140 days RangerRusset  ˜70 days  ˜90 days Umatilla Russet ˜110 days ˜125 days GemRusset ˜120 days ˜135 days

If potatoes are subject to reconditioning, the chemical agent istypically applied at the beginning of the reconditioning period. Thus,in some embodiments of the invention, the chemical agent is applied one,two, three, four or five weeks before potato tubers are processed tomake french fries or potato chips. In the practice of the methods of theinvention, the chemical agent may be applied to the potato tubers onmore than one occasion (e.g., at least twice) during the storage period.

Typically the chemical agent is applied simultaneously, or substantiallysimultaneously, to numerous, harvested, potato tubers. Potatoes may bestored in bulk storage sheds designed to hold anywhere from 5000 to25000 tons. The sheds are designed to precisely control ventilationthrough the bulk pile (which may be about twenty five feet deep) alongwith temperature and relative humidity. Temperature is controlled byventilation with outside air through air washers which also raises thehumidity. For example, the chemical agent can be volatilized at hightemperature and applied as a thermal fog into the storage ventilationsystem that circulates air through the potato pile, from bottom to top.The storage sheds are generally closed tight after fogging, and the airmay be circulated internally through the pile for several hours afterapplication of the chemical agent. Again by way of example, the chemicalagent can also be atomized and introduced into the ventilation system ofthe storage sheds. Drenches or dips can also be used to apply thechemical agent. The chemical agent can also be impregnated on filters,or other inert materials, to facilitate slow release over time throughthe ventilation system of the storage sheds. The chemical agent can alsobe applied as an emulsifiable concentrate for spraying onto fresh marketpotatoes as they go through sorting and packing lines prior to bagging.

The amount of chemical agent that is applied to the potato tubers iseffective to inhibit sprouting of the tubers. In some embodiments of themethods of the invention, sprouting is inhibited by at least 25%. Insome embodiments of the methods of the invention, sprouting is inhibitedby at least 50%. In some embodiments of the methods of the invention,sprouting is inhibited by at least 75%. In some embodiments of themethods of the invention, sprouting is inhibited by at least 90%. Insome embodiments of the methods of the invention, sprouting is inhibitedby at least 95%. In some embodiments of the methods of the invention,sprouting is inhibited by 100%.

The amount of chemical agent that is effective to inhibit sprouting ofthe potato tubers depends on such factors as the composition of thechemical agent and the potato cultivar being treated. In someembodiments of the methods of the invention, the chemical agent isapplied to the potato tubers in an amount sufficient to provide a dosageof the at least one carbonyl compound of from 0.001 mmol/kg potatotubers to 100.0 mmol/kg potato tubers. In some embodiments of themethods of the invention, the chemical agent is applied to the potatotubers in an amount sufficient to provide a dosage of the at least onecarbonyl compound of from 0.1 mmol/kg potato tubers to 5.0 mmol/kgpotato tubers. In some embodiments of the methods of the invention, theat least one carbonyl compound is a C₈ or C₉ aliphatic carbonylcompound, and the chemical agent is applied to the potato tubers in anamount sufficient to provide a dosage of the C₈ or C₉ aliphatic carbonylcompound of from 0.5 mmol/kg potato tubers to 1.0 mmol/kg potato tubers.In some embodiments of the methods of the invention, the at least onecarbonyl compound is a C₇ aliphatic carbonyl compound, and the chemicalagent is applied to the potato tubers in an amount sufficient to providea dosage of the C₇ aliphatic carbonyl compound of from 0.5 mmol/kgpotato tubers to 1.5 mmol/kg potato tubers. In some embodiments of themethods of the invention, the at least one carbonyl compound is a C₆aliphatic carbonyl compound, and the chemical agent is applied to thepotato tubers in an amount sufficient to provide a dosage of the C₆aliphatic carbonyl compound of from 0.5 mmol/kg potato tubers to 3.0mmol/kg potato tubers.

In this regard, when the chemical agent includes more than one α,βunsaturated aliphatic aldehyde and/or α,β unsaturated aliphatic ketone,the stated dosage refers to the combined amount of the aldehyde(s)and/or ketone(s).

The methods of the present invention are applicable to any potatocultivar including, but not limited to, Russet Burbank, Ranger Russet,Umatilla Russet, Shepody, Norkotah Russet, Yukon Gold, Norchip, GemRusset, Atlantic, Chipeta, Snowden, and Dark Red Norland.

The following examples merely illustrate the best mode now contemplatedfor practicing the invention, but should not be construed to limit theinvention. All literature citations herein are expressly incorporated byreference.

EXAMPLE 1

This Example shows that trans-2-hexenal inhibits potato tuber sprouting.

Methods: Desiree potatoes were produced in research plots at theEdmonton Research Station, University of Alberta in 1999. The tuberswere harvested in September, washed, transported to Washington StateUniversity and placed in 4° C. storage in late October. Tubers, selectedfor uniform size, were taken from the storage area for the experiment inJune. The 9-month-old tubers were fully emerged from dormancy after thisprolonged storage interval; however, no sprout growth had occurred atthe low storage temperature.

The tubers were washed, air-dried, and evenly divided between two 9.2liter (L) glass desiccators (8 tubers per desiccator). Trans-2-hexenal(200 μL) was pipetted into a 50 milliliter (mL) beaker that was placedinside one of the desiccators. The other desiccator served as control.Both desiccators were closed and the tubers were incubated in the twoatmospheres for 32 hours. The desiccators were then opened, anadditional 1000 μL of trans-2-hexenal was added to the beaker, and thedesiccators were closed for an additional 24 hours. One tuber from eachchamber was sampled for trans-2-hexenal content at the end of the 56hour treatment interval. The treated tubers were then planted in apeat/perlite/soil mix in 15-cm-diameter pots and placed in a greenhousewith no supplemental lighting at 21° C.

The experiment was set up in a randomized complete block design withtreatments (2 lines×2 [hexenal]) arranged factorially. Time to plantemergence was recorded and plants were harvested 21 days after planting.Plants were separated into various components (e.g., stems, leaves) atharvest and the effects of trans-2-hexenal on plant morphology wereassessed.

Results: as shown in FIGS. 1A-F, trans-2-hexenal clearly inhibitedsprouting, and thus plant emergence, and plant growth from potatotubers.

EXAMPLE 2

This Example shows the effect of cultivar identity and tuber exposuretime on inhibition of potato tuber sprouting by trans-2-hexenal.

Methods: Ten-month-old Ranger Russet, Umatilla and Russet Burbankseed-tubers were taken from 4° C. storage and treated withtrans-2-hexenal in 9.2-L glass desiccators as described in Example 1.The tubers were exposed to trans-2-hexenal for 0, 12 and 24 hours at 23°C. at a concentration of 4.7 mmol/kg potato tubers. Regardless ofexposure time, all tubers remained enclosed in the chambers for theentire 24 hour period. This was accomplished by introducing thetrans-2-hexenal at zero-time (into the 24 hour treatment desiccator) andafter 12 hour incubation (into the 12 hour treatment desiccator) througha septum in the top of the closed desiccator. The treated tubers wereplanted into moistened peat/perlite/soil potting mix and placed in thedark at 24° C. to stimulate sprouting. The experiment was set up in arandomized complete block design (5 replicates) with treatments (3cultivars×3 exposure times) arranged factorially. Effects oftrans-2-hexenal exposure and cultivar on etiolated sprout developmentand tuber quality were assessed 25 days after removal from the 4° C.storage.

Results: Tubers were photographed after 14 days and at harvest (25 days)to document effects on sprout development. As shown in Table 1, whilecultivar influenced the degree of sprouting, trans-2-hexenal effectivelyinhibited sprout development from all cultivars. As shown in Table 1,trans-2-hexenal damage to the periderm (skin) was dose and cultivardependent. The damage appeared as small pits of sunken tissueencompassing some of the lenticels. The severity of pitting increasedwith time of exposure to trans-2-hexenal and Russet Burbank tubers weremore resistant than Umatilla and Ranger Russet tubers. Soft rot lesionswere also apparent on trans-2-hexenal-treated tubers; however, this wasmore a consequence of tubers being buried in moist medium for 25 dayswithout sprouting than to a direct effect of trans-2-hexenal onsusceptibility to the soft rot organism. In fact, trans-2-hexenal hasbeen shown to inhibit bacterial growth on other harvested plantcommodities (Corbo et al., J. Agric. Food Chem. 48:2401-2408 (2000);Archbold et al., HortScience 34:705-707 (1999)).

As shown in Table 2, the concentrations of reducing sugars and sucrosewere substantially lower in trans-2-hexenal-treated Russet Burbanktubers compared with sprouted controls, supporting the use of thealdehyde as a reconditioning agent. Low sugars are a requisite tomaintaining processing quality.

TABLE 2 Hexenal Exposure (4.7 mmol/ Sprout Average External kg potatoFresh Sprout Pit Soft Rot Soluble Carbohydrates tubers) Weight LengthRating Lesions Suc Glu Fru Glu + Fru Cultivar (h) (g/tuber) (cm/tuber)(1-4 scale)* (no/tuber) (mg/g dry wt.) Umatilla 0 164 39.1 1.0 0 — — — —12 0 0 3.7 2.2 — — — — 24 0 0 4.0 2.6 — — — — Ranger 0 125 46.7 1.0 0 —— — — Russet 12 0 0 3.1 1.0 — — — — 24 0 0 3.7 1.2 — — — — Russet 0 12147.2 1.0 0 12.7 70.9 73.8 145 Burbank 12 0 0 1.8 0.6 6.30 19.0 19.5 38.524 0 0 2.2 0.4 6.28 16.5 17.8 34.3 U/R, B 0.01 0.01 — — — — — — R/B nsns — — — — — — U, R/B — — 0.01 0.05 — — — — U/R — — 0.05 0.05 — — — —Exposure 0.01 0.01 0.01 0.01 0.05 0.01 0.01 0.01 E_(LT) — — 0.01 0.010.05 0.01 0.01 0.01 E_(QT) — — 0.01 ns ns 0.01 0.01 0.01 E_(LT) × — — —— — — — — U/R, B E_(QT) × — — — — — — — — U/R, B E_(LT) × — — — — — — —— R/B E_(QT) × — — — — — — — — R/B E_(LT) × — — 0.01 0.05 — — — — U, R/BE_(QT) × — — 0.05 ns — — — — U, R/B E_(LT) × U/R — — ns ns — — — —E_(QT) × U/R — — ns ns — — — *1 = no pits; 2 = widely spaced and/or verysmall (<10%) pitted surface area; 3 = pitted surface area equal to10-50% of tuber surface; 4 = tuber surface uniformly pitted on all sides(>50% pitted).

The following abbreviations are used in Table 2: Umatilla (U); RangerRussett (R); Russett Burbank (B); sucrose (suc); glucose (glu); fructose(fru); exposure time linear trend (E_(LT)); exposure time quadratictrend (E_(QT)); centimeter (cm); gram (g); hour (h); number (no.); andmilligram (mg).

EXAMPLE 3

This Example describes the effect of trans-2-hexenal on potato tuberrespiration. Dormant tubers have a relatively low respiration rate,which is a desirable characteristic for prolonged storage. Lowrespiration conserves dry matter, minimizes vital heat, prevents CO₂buildup, and slows maturation and premature aging of tubers.

Methods: Eleven-month-old Russet Burbank seed-tubers were taken from a4° C. storage area and treated with 250 μL of trans-2-hexenal in a 9.2liter (L) glass desiccator (0.96 mmol/kg potato tubers) for 12 hours at23° C. The trans-2-hexenal was pipetted onto Whatman #1 filter paper ina glass petri dish (5.5 cm diameter) inside the desiccator. Controltubers were enclosed in a desiccator without trans-2-hexenal. Followingtreatment, the tubers were enclosed in 1 L nalgene chambers (3 tubersper chamber) that were placed at 15° C. A continuous airflow(approximately 80 mL/min; 21% O₂, 79% N₂) was established around thetubers through inlet and outlet ports in the lid of each chamber.Respiration rates were determined at four hour intervals over a 28 daystorage period by quantifying CO₂ in the outflow from each chamber witha LI-COR model 6262 infra-red gas analyzer (LI-COR Inc., Lincoln Nebr.).The experiment was set up in a randomized complete block design (5replicates) with two treatments (control and trans-2-hexenal-treated).The effect of trans-2-hexenal exposure on the development of etiolatedsprouts was assessed 28 days after removal from the 4° C. storage.

Results: The respiration rate of trans-2-hexenal-treated tubers was 38%greater (P>0.05) than untreated tubers immediately following the 12 hourtreatment period. Control tubers maintained a relatively constant rateof respiration (approx. 7.6 mL CO₂/kg/h) over the initial 64 hours ofstorage at 15° C. Respiration of trans-2-hexenal-treated tubers declinedrapidly over the initial 10 hours of storage, reaching a level that wasequal to the untreated tubers by 32 hours after treatment. Control andtrans-2-hexenal-treated tubers maintained equal rates of respirationthat declined steadily from 32 to 150 hours. Respiration rate of controltubers then gradually increased over the remainder of the 27 day storageinterval concomitant with sprouting.

In contrast, respiration of trans-2-hexenal-treated tubers continued tofall and was 2.5-fold lower than control tubers by the end of the study.As shown in Table 3, consistent with previous studies, trans-2-hexenalinhibited sprouting.

TABLE 3 Tuber Treatment trans-2-Hexenal Variable Untreated (0.96mmol/kg) Sprout fresh wt (g/tuber) 4.0 0**   Average sprout length(cm/tuber) 5.4 0**   Tuber external pit rating 1.0 2.2** Tuber fresh wtloss (g/tuber) 31.0 11.8**  **Significantly different from untreatedcontrol at P < 0.01.

The initially-high rate of respiration in hexenal-treated tubers may bebeneficial to quality, stimulating catabolism of excess reducing sugarsand thus reconditioning the tubers.

EXAMPLE 4

This Example compares the abilities of trans-2-hexenal, trans-2-heptenaland trans-2 octenal to inhibit sprouting in potato tubers.

Methods: Eleven-month-old Russet Burbank seed tubers were taken from a4° C. storage area and exposed to trans-2-hexenal (0.6-4.3 mmol/kg),trans-2-heptenal (0.6-3.8 mmol/kg) and trans-2-octenal (0.5-2.5 mmol/kg)vapors separately in 3.9 L glass containers for 12 hours at 23° C. Thealdehydes were applied to filter paper inside petri dishes within eachjar. Control tubers were enclosed in a glass container without anyaldehyde. Sprouts were ‘peeping’ (approximately 3 mm in length) at thetime of treatment. Following treatment, tubers were placed at 18° C.(95% relative humidity) in the dark to sprout for 26 days. Theexperiment was set up in a randomized complete block design (5replicates) with chemicals and concentrations arranged factorially.Effects of the aliphatic aldehydes on the development of etiolatedsprouts were documented at 20 days (photographically) and 26 days ofsprouting.

Results: All of the aliphatic aldehydes inhibited sprouting at allconcentrations tested. Comparisons among aldehydes at a particularconcentration were not possible in this study, as molar concentrationsin the vapor phases were not exactly equivalent (due to differences invapor pressures that were not considered in this study).

Effects of the aldehydes on sprout development and tuber quality at theend of the study (26 days) are reported in Table 4.

TABLE 4 Average Aldehyde Sprout Sprout External Pit Concentration FreshWeight Length Rating Treatment (mmol/kg) (g/tuber) (cm/tuber) (1-4scale)* Control — 7.70** 8.8** 1.0 trans-2- 0.63 0.04 0.2 1.4 Hexenal1.33 0 0 2.0 2.06 0 0 2.6 2.50 0 0 3.5 4.34 0 0 2.8 trans-2- 0.56 0.010.2 1.0 Heptenal 1.11 0 0 1.6 1.69 0 0 1.4 2.16 0 0 2.3 3.85 0 0 2.5trans-2- 0.50 0 0 1.0 Octenal 0.97 0 0 1.0 1.44 0 0 1.6 1.93 0.10 0.21.3 2.48 0.13 0.2 1.3 *1 = no pits; 2 = widely spaced and/or very small(<10%) pitted surface area; 3 = pitted surface area equal to 10-50% oftuber surface; 4 = tuber surface uniformly pitted on all sides (>50%pitted). **Significantly different from all other treatments at P >0.01.

External pitting of trans-2-hexenal-treated tubers was minimal at thelowest concentration, but increased significantly with concentration.Moreover, the extent of aldehyde-induced, external pitting of theperiderm decreased as carbon number increased(hexenal>heptenal>octenal).

EXAMPLE 5

This Example compares the efficacy of different concentrations of C₅ toC₉ trans-2 aldehydes at inhibiting sprouting of Russet Burbank andRanger Russet potato tubers over a prolonged storage period.

Methods: Four-month-old Russet Burbank and Ranger Russet seed-tuberswere taken from a 4° C. storage area and treated (Jan. 10, 2001)separately with 0, 0.5, 0.75 and 1.0 mmol/kg tuber of trans-2-pentenal,trans-2-hexenal, trans-2-heptenal, trans-2-octenal, and trans-2-nonenalin 3.9 L glass jars. The volume of inhibitor required to achieve theabove rates was pipetted onto filter paper discs inside the lids of eachjar. The concentration of inhibitors in the headspace of the jars wasequal at 0.16 mmol/L. The tubers were enclosed in the jars and thusexposed to inhibitor vapor for 24 hours at 23° C. Control tubers wereenclosed in a glass jar without any aldehyde. Following treatment,tubers were removed from the jars and placed at 8° C. (46° F.) (95%relative humidity) in the dark to sprout for 120 days (17 weeks). Theexperiment was set up in a randomized complete block design (5replicates) with chemicals and concentrations arranged factorially.Effects of the aliphatic aldehydes on the development of etiolatedsprouts were documented photographically and quantitatively (sproutnumber and fresh weight) after 120 days of storage.

Results: Comparisons between aldehydes for their ability to inhibitsprouting is possible in this study as aldehydes were applied atequivalent molar concentrations on a tuber weight (kg) and headspacebasis. The degree of inhibition of sprouting after 17 weeks (4 months)of storage at 8° C. depended on aldehyde and concentration (see FIGS.2A-D).

Trans-2-octenal and trans-2-nonenal totally inhibited sprout developmentat all concentrations. Moreover, these two aldehydes did not induceexternal pitting damage to the periderm relative to that induced by theC₅ to C₇ aldehydes. C₅, C₆ and C₇ aldehydes inhibited sprouting in aconcentration-dependent manner and, in general, the degree of inhibitionat a particular concentration increased with increased carbon chainlength of the aldehyde (C₈ and C₉>C₇>C₆>C₅).

EXAMPLE 6

This Example shows the efficacy of trans-2-nonenal as a sprout inhibitorto facilitate reconditioning, and thus improve processing quality oftubers that had developed high sugar levels during storage at lowtemperatures.

Methods: Russet Burbank tubers were stored at 7° C. (44° F.) fromharvest Oct. 29, 2000 to Jan. 26, 2001. The tubers were transferred to4° C. (40° F.) on Jan. 26, 2001, until treatment on Apr. 2, 2001. Tuberswere treated with 0.45 mmol/kg trans-2-nonenal in 9.2 L glassdesiccators for 17 hours at 23° C. Following treatment, the tubers wereplaced at 14° C. (57° F.) to recondition for 0, 1, 2, 3 and 4 weeks.French fries were processed from the reconditioned tubers by fryinglongitudinal slices (⅜″ thick×1⅛″ wide) of potato tuber in 375° F. (190°C.) oil for 3.5 minutes. Fry darkness of the apical and basal ends ofthe fries was quantified with a photovolt reflectance meter within threeminutes of frying. A high reflectance reading (photovolt unit) indicateslight fry color due to a relatively low sugar level and thus ahigh-quality processed product. Conversely, a low reflectance readingindicates dark fry color due to high sugar content, resulting in lowprocessing quality. Treatments (plus and minus trans-2-nonenal; 5reconditioning times) were arranged factorially in a randomized completeblock design with 12 replicates. Sprout fresh weight and fry color wererecorded.

Results: Color of fries from unconditioned (i.e., zero reconditioning)control and trans-2-nonenal-treated tubers was unacceptably darkfollowing low temperature storage (see FIG. 3). Fry color becameprogressively lighter (higher photovolt units) as reconditioning time at57° F. increased, indicating a significant improvement in processingquality of both control and trans-2-nonenal-treated tubers. Theprocessing quality of control tubers, however, declined from 2 to 4weeks of reconditioning, while that of trans-2-nonenal-treated tuberscontinued to increase (see FIG. 3). These effects were attributable todifferences in sprout development over the four week reconditioningperiod at 57° F. Control tubers produced about four fold more sprouts(50.4 g fresh weight/12 tubers vs. 13.5 g fresh weight/12 tubers) thantrans-2-nonenal-treated tubers at four weeks of reconditioning.Trans-2-nonenal-induced inhibition of sprouting thus facilitated moreextensive reconditioning and improvement of processing quality of tubersover the four week interval.

While the preferred embodiment of the invention has been illustrated anddescribed, it will be appreciated that various changes can be madetherein without departing from the spirit and scope of the invention.

1. A method for inhibiting sprouting of potato tubers, the methodcomprising the step of contacting a potato tuber with an amount of achemical agent comprising at least one aliphatic carbonyl compoundselected from the group consisting of a C₃ to C₁₄, α,β unsaturatedaliphatic aldehyde and a C₄ to C₁₄, α,β unsaturated aliphatic ketone,wherein the amount of the chemical agent is effective to inhibit potatotuber sprouting.
 2. The method of claim 1 wherein the aliphatic aldehydeis defined by formula I and the aliphatic ketone is defined by formulaII: wherein:

the aliphatic aldehyde of formula I is C₃ to C₁₄; the aliphatic ketoneof formula II is C₄ to C₁₄; R₁ is H or branched or unbranched,substituted or unsubstituted C₁-C₁₁ lower alkyl, or branched orunbranched, substituted or unsubstituted C₁-C₁₁ lower alkenyl; R₂ isbranched or unbranched, substituted or unsubstituted C₁-C₁₁ lower alkyl,or branched or unbranched, substituted or unsubstituted C₁-C₁₁ loweralkenyl; and R₃ is H or branched or unbranched, substituted orunsubstituted C₁-C₁₀ lower alkyl, or branched or unbranched, substitutedor unsubstituted C₁-C₁₀ lower alkenyl.
 3. The method of claim 2 whereinthe chemical agent comprises an aliphatic aldehyde defined by formula I.4. The method of claim 3 wherein the aliphatic aldehyde is selected fromthe group consisting of trans-2-pentenal; trans-2-hexenal;trans-2-heptenal; trans-2-octenal; trans-2-nonenal; trans-2-decenal;trans-2-undecenal; trans-2-dodecenal; trans-2,4,-nonadienal; trans-2,cis-6-nonadienal; and trans-3-nonen-2-one.
 5. The method of claim 4wherein the aliphatic aldehyde is trans-2-pentenal.
 6. The method ofclaim 4 wherein the aliphatic aldehyde is trans-2-hexenal.
 7. The methodof claim 4 wherein the aliphatic aldehyde is trans-2-heptenal.
 8. Themethod of claim 4 wherein the aliphatic aldehyde is trans-2-octenal. 9.The method of claim 4 wherein the aliphatic aldehyde is trans-2-nonenal.10. The method of claim 4 wherein the aliphatic aldehyde istrans-2-decenal.
 11. The method of claim 4 wherein the aliphaticaldehyde is trans-2-undecenal.
 12. The method of claim 4 wherein thealiphatic aldehyde is trans-2-dodecenal.
 13. The method of claim 4wherein the aliphatic aldehyde is trans-2,4,-nonadienal.
 14. The methodof claim 4 wherein the aliphatic aldehyde is trans-2, cis-6-nonadienal.15. The method of claim 4 wherein the aliphatic aldehyde istrans-3-nonen-2-one.
 16. The method of claim 2 wherein the chemicalagent comprises an aliphatic ketone defined by formula II.
 17. Themethod of claim 1 wherein the amount of chemical agent is sufficient toprovide a dosage of the at least one carbonyl compound of from 0.001mmol/kg potato tubers to 100 mmol/kg potato tubers.
 18. The method ofclaim 1 wherein the amount of chemical agent is sufficient to provide adosage of the at least one carbonyl compound of from 0.1 mmol/kg potatotubers to 5.0 mmol/kg potato tubers.
 19. The method of claim 1 whereinthe chemical agent comprises a C₃ to C₁₄, α,β unsaturated aliphaticaldehyde, and the amount of chemical agent is sufficient to provide adosage of the aliphatic aldehyde of from 0.001 mmol/kg potato tubers to100 mmol/kg potato tubers.
 20. The method of claim 1 wherein thechemical agent comprises a C₃ to C₁₄, α,β unsaturated aliphaticaldehyde, and the amount of chemical agent is sufficient to provide adosage of the aliphatic aldehyde of from 0.1 mmol/kg potato tubers to5.0 mmol/kg potato tubers.
 21. The method of claim 20 wherein thealiphatic aldehyde is C₈ or C₉ and the amount of chemical agent issufficient to provide a dosage of the aliphatic aldehyde of from 0.5mmol/kg potato tubers to 1.0 mmol/kg potato tubers.
 22. The method ofclaim 20 wherein the aliphatic aldehyde is C₇ and the amount of chemicalagent is sufficient to provide a dosage of the aliphatic aldehyde offrom 0.5 mmol/kg potato tubers to 1.5 mmol/kg potato tubers.
 23. Themethod of claim 20 wherein the aliphatic aldehyde is C₆ and the amountof chemical agent is sufficient to provide a dosage of the aliphaticaldehyde of from 0.5 mmol/kg potato tubers to 3.0 mmol/kg potato tubers.24. The method of claim 1 wherein the chemical agent comprises a C₄ toC₁₄, α,β unsaturated aliphatic ketone, and the amount of chemical agentis sufficient to provide a dosage of the aliphatic ketone of from 0.001mmol/kg potato tubers to 100 mmol/kg potato tubers.
 25. The method ofclaim 24 wherein the amount of chemical agent is sufficient to provide adosage of the aliphatic ketone of from 0.1 mmol/kg potato tubers to 5.0mmol/kg potato tubers.
 26. The method of claim 24 wherein the aliphaticketone is C₈ or C₉ and the amount of chemical agent is sufficient toprovide a dosage of the aliphatic ketone of from 0.5 mmol/kg potatotubers to 1.0 mmol/kg potato tubers.
 27. The method of claim 24 whereinthe aliphatic ketone is C₇ and the amount of chemical agent issufficient to provide a dosage of the aliphatic ketone of from 0.5mmol/kg potato tubers to 1.5 mmol/kg potato tubers.
 28. The method ofclaim 24 wherein the aliphatic ketone is C₆ and the amount of chemicalagent is sufficient to provide a dosage of the aliphatic ketone of from0.5 mmol/kg potato tubers to 3.0 mmol/kg potato tubers.
 29. The methodof claim 2 wherein the chemical agent consists essentially of analiphatic aldehyde defined by formula I.
 30. The method of claim 2wherein the chemical agent consists essentially of an aliphatic ketonedefined by formula II.
 31. The method of claim 1 wherein the potatotuber is from a cultivar selected from the group consisting of RussetBurbank, Ranger Russet, Umatilla Russet, Shepody, Norkotah Russet, YukonGold, Norchip, Gem Russet, Atlantic, Chipeta, Snowden, and Dark RedNorland.
 32. The method of claim 1 wherein the potato tuber is contactedwith the chemical agent during a time period extending from harvest ofthe tuber to one week prior to utilization by a processor or a consumer.33. The method of claim 32 wherein the potato tuber is contacted withthe chemical agent within one month after harvest.
 34. The method ofclaim 32 wherein the potato tuber is contacted with the chemical agentwithin two months after harvest.
 35. The method of claim 32 wherein thepotato tuber is contacted with the chemical agent within one monthbefore utilization by a consumer.